Densitometer is an instrument used for measuring optical or photographic density. It is aimed at photoelectrical cell and is said to be a light source that defines the ratio of the radiant flux absorbed by a body to that incident upon it. It is used for printer’s calibration for desired results. Densitometer has three types named as transmission, combination and reflection.

Diagometer is an instrument used for measuring electrical conductivity, the power of electricity transmitted from various electrical bodies. It is like an electroscope which consists of a magnetic pointer and a dry pile to measure conductivity power.

Dioptometer is an instrument used for measuring ocular focus or refraction of the eyes. It is used in visual telescope system for quality image, which determines magnitude and different omitting signs from any light source.

Drumometer is an instrument used for measuring speed, mostly used by drummers. It tells the technical accuracy and speed of drummers on four primary devices, how fast and accurate they strike the drum in a specific time period.

Durometer is an instrument used for measuring hardness of substance. It has got huge applications and is used in measuring the hardness of so many things keeping certain standards, like mattress foams filled with resilient material, tyers, plastics and all those non-metallic things. It is available in both analog and digital models.

Ellipsograph is an instrument used for describing ellipses. This simple but technical instrument is able to make ellipses of any size from 0*0 to 170*110. Fine special pencil is required to work with this device.

Dynamometer is an instrument used for measuring mechanical force and power of any running engine or any motor. Both the torque produced by the movement of any electromechanical device and the power require to generate force, can be calculated and measured by dynamometer. Most common example of dynamometer is to generate a light by cycling.

Electroretinograph abbreviated as ERG is an instrument used for measuring electrical activity in the retina which are light sensitive cells and are termed as rod and con. When the retina generates electrical potential in the eye, Electroretinograph is put over the eye having electrodes that will contact with the electrical charge, when retina is stimulated by light. It is useful to find out abnormalities in retina and at the back side of eye.

Effusiometer is an instrument used for comparing molecular weights of gases. It tells the velocity and flow of gases under pressure as well as the amount per unit size.

Elatrometer is an instrument used for measuring gaseous pressure. It tells the amount of air density in any air pump.